1. Field of the Invention
This invention relates generally to diapers and more particularly to an improved disposable diaper having a close, sealing fit in the crotch area without causing dicomfort to an infant clad therewith.
2. Description of the Prior Art
Conventional disposable diapers generally comprise in order, a rectangular back sheet of hydrophobic waterproof i.e., water impervious material, a rectangular absorbent pad serving as a waste fluid reservoir and a rectangular top or face sheet of water pervious, generally hydrophobic material. In general, the back sheet is somewhat larger, ie, its longitudinal edges extend beyond the longitudinal edges of the absorbent pad layer and the water pervious layer. Conventional disposable diapers are prepared according to one of a number of prefolded configurations, to provide a narrowed portion in the crotch area to improve fit, appearance and diaper performance such as absorptive capacity.
The diaper should possess sufficient strength and particularly resistance to tearing in the crotch area, where it is often subjected to the bulk of the stresses resultant upon physical activity of the diaper-clad infant. Conversely the diaper must be readily capable of being closely but comfortably fitted to the physical contour of the infant with a minimum of effort and inconvenience to the mother. Close fit is essential to create a seal to contain discharged waste fluids to thus allow the absorbent pad layer sufficient time to absorb the waste fluid.
According to one known diaper assembly structure, the flap portions of the back sheet or water impervious layer are folded around the longitudinal edges of the absorbent pad and secured to the face sheet by adhesive. This provides a uniform "double" thickness along the longitudinal edges of the diaper and thus enhances the strength and tear resistant properties of the diaper in this area. However, these diapers are rather cumbersome and awkward to apply. Moreover, the bulky nature of the diaper leads to local buckling and bulging of the back sheet away from the thighs and trunk of the infant with consequent loss of sealing contact.
Additionally, the "double" thickness portion of the diaper tends to significantly reduce the efficiency of air circulation thorughout the diaper material. Heat dissipation is thus rendered highly inefficient, which can lead to infant discomfort, chaffing and heat rash, and the like. The problem is further aggravated since the folded-over portion of the back sheet is relatively large, thereby reducing the effective absorptive area of the diaper in the crotch portion. This can actually increase dripping of excess waste fluid.
Diapers folded in a box pleat configuration are also known. Generally, however, the panels defined by the box pleated diaper are spaced substantially from each other, requiring that the central panel behind the pleated panels receive most of the waste fluid. To provide the desired absorptive capacity, diapers of this construction sag away from the trunk of the body impairing proper utilization of the absorptive capabilities of the diaper.
Diapers of the aforedescribed type are generally provided with four longitudinal folds and are conventionally termed "wing-fold" diapers. Aside from certain objectionable performance characteristics, there diapers do not tend to lie flat a completely open position. This causes considerable problems when attempting to dress the infant since the diaper tends to bulge, bow, etc. making a close fit highly difficult.